We now have the outlines of a surprisingly powerful naturalist conception of God. Because my concern is theological, I shall not develop a full naturalistic philosophy. Such an enterprise is unnecessary because almost all contemporary philosophy is already naturalist in a broad sense. Still, we need a general description of the naturalist position which lies in the background of this project. There have been many forms of naturalism. The strongest, most austere form remains the one deriving from classical, Democritian materialism, today termed physicalism. Since I want to emphasize the constraints naturalism places upon theological formulation, I shall adopt a physicalist version of naturalism, one defended recently with elegance and power by John F. Post in The Faces of Existence.

Loosely, physicalism states that only the basic objects of mathematical physics exist and that everything at a higher or more complex level can occur only if there is a corresponding occurrence at the level of physics. Physicalism requires a realist conception of truth because some naturalisms such as positivism and pragmatism define truth non-realistically by appeal to practical success (for instance, experimentation or predictability), thereby remaining agnostic about the ontological status of theoretically defined non-observable entities and leaving the referential status of physical science indeterminate. Their understanding of natural science is consequently epistemic alone. Physicalism, in contrast, says that finally it is the world or existence (not scientific practice) that defines what is known in physics.